With recent evolvement of electronic devices, it has become a trend to develop memory devices having larger data storage capacity. In order to save data after the power is turned off, non-volatile memories, such as flash memory or ferroelectric random access memory (Fe-RAM), have received more attention. However, in order to process high-speed and large-capacity data, it is necessary to further develop a memory device which operates faster and has larger data storage capacity.
Furthermore, the ferroelectric material used in a conventional memory device is usually a material having a perovskite structure. A thickness of the ferroelectric material layer having the perovskite structure has to be greater than 200 nm to allow the ferroelectric material layer to exhibit a ferroelectric characteristic, so that the size of a ferroelectric field effect transistor (FeFET) is difficult to be reduced.
However, to replace the material having the perovskite structure with other ferroelectric materials, it is necessary to ensure that the ferroelectric characteristic of the ferroelectric material is unaffected during the fabrication processes or remains unchanged with increase of usage time, otherwise writing, reading and storing of data may be affected. Accordingly, the conventional memory device leaves room for improvement.